A cloud communication center network technology has been introduced to more efficiently utilize network resources. The cloud communication center network technology may greatly reduce operational expenditure and power consumption while increasing radio data capacity. Due to such advantages, the cloud communication center network technology has attracted much attention. Such a cloud communication center network technology may be referred to as a virtual radio network technology.
Typically, a radio unit and a digital unit are implemented as single equipment and installed at a base station. The digital unit is connected to a switching system located at a central office, the radio unit transmits and receives a radio signal to/from a user equipment, and the digital unit processes the radio signal in accordance with an open system interconnection model (OSI) such as a radio Internet protocol.
Unlike the typical base station equipment, a cloud communication center network includes a digital unit and a radio unit that are separate and generally installed at different locations. The cloud communication center network may be referred to as a virtual radio network. For example, a radio unit may be installed at a base station in a respective target service area, and a plurality of digital units may be centralized in a digital unit center at a central office with a switching system. The radio unit may be coupled to a corresponding one of the digital units in the digital unit center through an optical interface. The radio unit may be coupled to repeaters. The radio unit may be coupled to one repeater or multiple repeaters. Such repeaters may deliver signals from user equipment to the radio unit and/or from the radio unit to the user equipment.
An orthogonal frequency division multiplexing (OFDM) technology has been employed in communication networks. The OFDM technology may use multiple paths for transmitting and receiving signals so inter-carrier interference and inter-symbol interference may be generated. In order to prevent such inter-carrier interference and inter-symbol interference, a guard interval is added between active symbol periods and a cyclic prefix is transmitted during the guard interval. When related signals arrive within one cyclic prefix, inter-carrier interference and inter-symbol interference are not generated so as to restore an original signal by combining related signals.
As described, a radio unit may be coupled to a plurality of repeaters. Such a radio unit may receive signals from a digital unit, process the received signal, and transmit the processed signals to user equipment. When the radio unit transmits signals to user equipment, the radio unit may transmit directly to the user equipment and/or indirectly to the user equipment through at least one repeater. Due to the OFDM, related signals may need to arrive at the user equipment within one cyclic prefix in order to enable the user equipment to restore an original signal without inter-symbol interference and inter-carrier interference. Due to the repeaters, signals indirectly delivered to the user equipment may be delayed.
Similarly, user equipment may transmit signals directly to a radio unit and/or indirectly to the radio unit through at least one repeater. Such signals may need to arrive at the radio unit within one cyclic prefix in order to enable the radio unit to combine the received related signal without inter-symbol interference and inter-carrier interference. Due to the repeaters, signals indirectly delivered to the radio unit may be delayed.